RE: [ECOS] Change output stream for printf

["Nicolas Brouard" <nicolas dot brouard at silicomp dot ca>]

Hi,
I would like to use the tty driver (specially the CYG_TTY_OUT_FLAGS_CRLF
functionnality) over a socket.
When I use serial port for printf, I have this simplified callgraph:
	printf
	-> puts (stdioinlines.cxx)
	-> fputs (fputs.cxx)
	-> StdioStream::write (stream.cxx)
	-> write (io.cxx)
	-> dev_fo_write (devfs.cxx)
	-> tty_write (tty.c)
	-> serial_write (serial.c)

With the socket (after dup2(socket_descriptor, stdout_no)), I have this
simplified callgraph:
	printf
	-> puts (stdioinlines.cxx)
	-> fputs (fputs.cxx)
	-> StdioStream::write (stream.cxx)
	-> write (io.cxx)
	-> bsd_write (sockio.c)

And I would like to use tty. So how can I have that?
	printf
	-> puts (stdioinlines.cxx)
	-> fputs (fputs.cxx)
	-> StdioStream::write (stream.cxx)
	-> write (io.cxx)
	=> dev_fo_write (devfs.cxx)
	=> tty_write (tty.c)
	-> bsd_write (sockio.c)

Another question: I don't find in the sources where is defined printf.
I found printf(const char *format, ...) which calls vfnprintf, but I didn't
find the printf which calls puts. In fact, when I call printf with one
argument, the second form is used. Where is this defined?

Thanks in advance.

Nicolas Brouard

-----Original Message-----
From: Nicolas Brouard [mailto:nicolas.brouard@silicomp.ca]
Sent: Monday, November 15, 2004 2:22 PM
To: Nick Garnett; Andrew Lunn
Cc: eCos Discussion
Subject: RE: [ECOS] Change output stream for printf


Thank you very much.
The redirection (or pipe) mechanism of *NIX works !
This is my code:
// Create a socket
socket(...);
bind(...);
listen(...);
int socket_descriptor = accept(...);

// Duplicate socket_descriptor to stdout descriptor
int stdout_no = fileno(stdout);
close(stdout_no);
dup2(socket_descriptor, stdout_no); // dup(socket_descriptor) works as well

printf("This is printed over the socket\n");
diag_printf("This is printed over serial port\n");

Nicolas Brouard

-----Original Message-----
From: Nick Garnett [mailto:nickg@ecoscentric.com]
Sent: Monday, November 15, 2004 1:51 PM
To: Andrew Lunn
Cc: Nicolas Brouard; eCos Discussion
Subject: Re: [ECOS] Change output stream for printf


Andrew Lunn <andrew@lunn.ch> writes:

> > Another approach would be to use fileno(stdout) to get the file
> > descriptor underneath stdout (it should be 1). close() it and then
> > dup2() the socket into that descriptor. This is how it is done in *NIX
> > and it should work in eCos. You may need to do a bit of business to
> > flush any data still in the stream buffers.
>
> I seemed to remember something about this not working, which i why i
> did not suggest it. Now you have mentioned it, i went googling. Its
> probably worth reading the thread:
>
> http://sources.redhat.com/ml/ecos-discuss/2003-04/msg00135.html

Yes, I recall that not working as expected. Which is why my approach
manipulates the file descriptors underneath the C library, rather than
mess with the C library itself. If this is done early on in the
program, before any output is generated, it is logically equivalent to
redirecting or pipelining a *NIX application in the shell.

--
Nick Garnett                    eCos Kernel Architect
http://www.ecoscentric.com/     The eCos and RedBoot experts




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